Thursday, October 28, 2010

October 1. West Yellowstone, Wyoming. A Minor Geyser While We Wait For Old Faithful.

Most of the pictures in the last post
about hot springs and fumeroles (steam vents)
were taken as we were driving through Yellowstone.
Mr. Hawthorne didn't want to stop
since we were on our way to see Old Faithful.
I was reading my AAA guide
which said the interval between eruptions
can be as long as 95 minutes.
Hence, Mr. Hawthorne's hurry.
The way our luck is,
we figgered we'd get there right as
Old Faithful was winding down,
then have to wait until the next eruption.
As it happened,
we had very little wait time for Old Faithful
and we were first treated to a minor geyser's eruption.
Approaching the geyser basin.
At 3:19.
But first,
some hydrothermal explanation.
Sprinkled amid all the hot springs in Yellowstone
are the rarest fountains of all -
the geysers.
What makes them rare and distinguishes geysers
from hot springs is that somewhere,
usually near the surface in the plumbing system,
there are one or more constrictions
preventing water from freely circulating
to the surface where heat could escape.
The surrounding pressure increases with depth
and the increased pressure exerted by the
tremendous weight of the overlying rock and water
prevents the water from vaporizing.
Expanding steam bubbles from rising hot water
build up behind these constrictions,
ultimately squeezing through the narrow passageways
and forcing the water above to overflow from the geyser.
Bubbling upward, the steam expands as it nears the top
of the water column until the bubbles are too large
and too numerous to pass freely through the constrictions.
At a critical point,
the confined bubbles actually lift the water above,
causing the geyser to splash or overflow.
The release of water at the surface prompts
a sudden decrease in pressure of the hotter waters
at great depth, triggering a violent chain reaction
of tremendous steam explosions in which the volume
of rising, now boiling, water expands 1500 times or more.
This expanding body of boiling superheated water
bursts into the sky,
resulting in one of Yellowstone's famous geysers.
Water is expelled faster than it can enter the geyser's
plumbing system, and the heat and pressure gradually decrease.
The eruption stops when the water reservoir is depleted
or the gas bubbles diminish enough to be able
to rise without ejecting the water.
As I've said before,
there are more geysers here at Yellowstone
than anywhere else on earth.
We only had time here to go to one of the geyser basins -
that of Old Faithful.
While waiting for Old Faithful,
we were able to witness a smaller, minor geyser.
Enjoy.

The time print on my camera
started at 3:38 in the first photograph
and ended at 3:42 in the last photograph.